Amid the heat and humidity of the monsoon season, Hannah Foster's parents sat in a packed room at the Press Club in Delhi and pleaded with the Indian media to help track down their daughter's killer.

"We come to you in desperation, seeking help... Every parent in India will share our anguish at the cruel loss of a loved and loving daughter," said Trevor Foster, as he sat beside his wife Hilary, on that day more than four years ago. Sixteen months after their 17-year-old Hannah had been kidnapped, raped and murdered, this personal mission 4,000 miles across the world was, Hampshire detectives secretly feared, futile.

Maninder Pal Singh Kohli, 41, the key suspect who yesterday was finally convicted, had fled four days after the killing to his native Chandigarh in Punjab, and then continued to travel, adopting various aliases. Hampshire officers questioned whether he would really be found in the vast country. Neither the family nor the police could have anticipated how swiftly the story would captivate India. Days later, on the other side of India from Chandigarh, in the poor farming community of Kalimpong, West Bengal, five people spotted Kohli's picture in a newspaper and contacted police. Among them was a former British Army Gurkha, Roshan Gurung, who would be a key witness at the trial.

It was just one hurdle surmounted by Hannah's parents, a cardiac nurse and an auditor, in their journey to see the man who took away their "precious and fragile" daughter put behind bars. The Fosters refused to back down, despite Hilary's battle with breast cancer, Kohli's refusal to return to the UK, and frustrations of the Indian legal system.

After a plea to the British media (with reward of £65,000) failed, they decided to make the first of three trips to India on 10 July 2004. Kohli, it later emerged, initially lay low in Chandigarh, where his younger brother was a policeman, but fled when British police arrived weeks later. For seven months he lived in Bangalore, where he claimed to be a tourist called Mike Dennis. When people became suspicious, he escaped to Darjeeling. As detectives offered five million rupee (approximately £60,000) for information leading to his arrest, he found a new home and took a second wife. Kohli kept in contact with his brothers by email, shaved off the beard of his Sikh religion and planned to cross into his new wife's native Nepal, which has no extradition treaty with the United Kingdom. But his plan was cut short when he was recognised by Mr Gurung, the former Gurkha.